Seed cup assemblies are used in combination with seeding implements in order to meter seed or granular fertilizer through tubes and into the ground. Their use is normally combined with some form of ground opening device. Seed cup assemblies are used with pneumatic seeders and, in the present application, each of the large hoppers uses one seed cup assembly for metering seed into the air stream of the pneumatic system which blows the seed to the location of the ground openers through a network of flexible hoses. Conventional seed cup assemblies have proven to be unsatisfactory when used with the pressurized pneumatic seeders, primarily due to the problem of seeds leaking under pressure from the cup housing and into the air stream of the system.